Japan on Thursday protested to Beijing a second time over the entry of two Chinese fishery patrol boats into waters near disputed Japanese-administered islands, the foreign ministry said.

Japanese Foreign Minister Takeaki Matsumoto lodged the renewed protest with the Chinese ambassador to Japan, Cheng Yonghua, the ministry said.

The move comes after the long-standing territorial row over the islands -- called Senkaku in Japan and Diaoyu in Chinese -- intensified early Wednesday.

The Japan coastguard said two Chinese fisheries patrol boats entered a 12-nautical-mile zone around the islands which Tokyo considers its territorial waters.

The islands -- also claimed by Taiwan -- have been the source of diplomatic rows at a time when Japan has also voiced concern about China's growing naval power.

Matsumoto told Cheng that it was "deeply regrettable" that the two Chinese patrol boats entered the waters in the East China Sea, the ministry said in Thursday's statement.

The envoy said he will immediately convey the minister's protest to Beijing but repeated China's position on the islands, the statement said.

On Wednesday, Japan's Vice Foreign Minister Kenichiro Sasae had summoned Cheng and protested the incident a first time.

Chief Cabinet Secretary Yukio Edano also said on Wednesday: "Japan reiterated that there is no question that the Senkaku islands are an integral part of Japanese territory, historically and under international law."

China's foreign ministry spokesman Ma Zhaoxu immediately said the boats were on a routine patrol and re-iterated Beijing's claim over the islands, state media reported.

In September last year, Beijing broke off all high-level contact with Tokyo after Japan detained a Chinese fishing boat captain whose vessel had collided with Japanese coastguard patrol ships in the same waters.

Japan eventually released the captain under strong pressure from China, a move that helped eased the tension.

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